Among the immediate goals of the Human Genome Project are to develop a framework map of index markers spaced an average of 2-5 centiMorgans apart. Longer term goals include the preparation of physical maps of all human chromosomes consisting of markers spaced at 100kb intervals and overlapping sets of cloned DNA such as cosmid and yeast artificial chromosome clones. It is clear that mapping at this level will be a joint endeavor, requiring the cooperation of many investigators, and the commitment of a number of laboratories with complementary resources. The physical and genetic mapping of chromosome 18 has lagged behind other chromosomes since such mapping is usually disease driven (the localization of a disease gene to a particular region of the chromosome). However, there has been increased interest in the physical mapping of chromosome 18 with the identification of a susceptibility gene for manic-depressive illness to 18p, refined mapping of the X; 18 translocation in synovial sarcoma, and mapping of Nieman-Pick type C to 18q to name a few. To exchange up-to-date information, and to foster and improve collaborations among the interested groups, we propose an Third International Workshop on Chromosome 18 to continue the collaborative efforts that were made during the first two workshops. This conference grant will allow for the continued interactions of researchers who have an interest in the physical and genetic maps of chromosome 18 and the inclusion of new scientists that are interested in improving the physical and genetic map for chromosome l8. The Aims of the Workshop are: 1. To prepare consensus genetic and physical maps of chromosome 18 2. To assess resources available for mapping chromosome 18 3. To assemble a collection of STS that are spaced along the chromosome 4. To foster collaborations among interested investigators 5. To interface with the chromosome 18 committee of the Human Gene Mapping Workshops, and with the CEPH and Eurogem representatives for chromosome 18.